The present invention relates to a semiconductor light emitting device for taking out a light emitting output in a direction substantially perpendicular to a semiconductor substrate.
In general semiconductor light emitting device, it is necessary to electrically separate light emitting elements from each other to prevent crosstalk between the adjacent elements so as to form the elements in an array. The elements are electrically separated from each other by forming a groove for separation between the elements. When such a groove is formed by wet etching, a groove having a specified face in a specified direction is formed by the anisotropy of a crystal so that the width, depth and direction of the groove cannot be independently controlled. Accordingly, such a construction is not suitable for the integration of high density with respect to the arrayed elements and the arbitrariness of design.
As mentioned above, to construct the light emitting diode suitable for a one or two-dimensional array of high density, it is necessary to provide a structure in which the size of the light emitting portion is small and a sufficient light output is obtained and the injecting efficiency of the electric current is high and the light emitting efficiency is also high. Further, such a structure must have a high mechanical strength with respect to the element. Further, it is necessary to perform the electrical separation of the elements suitable for the high density array having less crosstalk between the adjacent elements. In addition, it is preferable that the light emitting angle is small.
A compound semiconductor laser has been recently researched by various kinds of methods. A proposed compound semiconductor laser has various kinds of stripe type structures to reduce an oscillating threshold value electric current and enable the operation of the laser in a single transversal mode. For example, there is a Melt-Etched Inner Stripe (MEIS) type laser element as a laser element of an inner stripe type having a structure for concentrating the electric current within the laser element.
In this MEIS type laser element, for example, an n-GaAs buffer layer formed by a liquid phase epitaxial growing method, an n-Al.sub.0.45 Ga.sub.0.55 As clad layer, an undoped Al.sub.0.15 Ga.sub.0.85 As active layer, a p-Al.sub.0.45 Ga.sub.0.55 As clad layer, and a p-GaAs cap layer are sequentially formed on an n-GaAs substrate. An n-GaAs layer and an n-Al.sub.0.45 Ga.sub.0.55 As layer having a groove in a backward mesa shape are formed on the side of the active layer of the p-Al.sub.0.45 Ga.sub.0.55 As clad layer. A p-type ohmic electrode is formed on the p-GaAs cap layer on an upper face of a stacked portion, and an n-type ohmic electrode is formed on the rear face of the substrate. In this general element structure, the n-GaAs layer and the n-Al.sub.0.45 Ga.sub.0.55 As layer formed in the p-Al.sub.0.45 Ga.sub.0.55 As clad layer act as a layer for concentrating the electric current thereon. In this electric current blocking layer, the n-GaAs layer is formed in an upper portion of the active layer through the p-Al.sub.0.45 Ga.sub.0.55 As clad layer having a very thin thickness less than about 0.3 .mu.m. Therefore, a layer portion except for the groove formed in the backward mesa shape constitutes a loss region to stabilize the transversal mode.
However, in such a structure, two electric current blocking layers and the p-Al.sub.0.45 Ga.sub.0.55 As clad layer as an electric current channel, and the p-GaAs cap layer are stacked with each other in an upper portion of the active layer so that the entire thickness of the stacked layers approximately becomes 7 .mu.m. When such an element is manufactured, it is necessary to etch the n-GaAs layer by meltback during the liquid phase growth so as to form the groove in the backward mesa shape. Therefore, the manufacturing process is complicated and it takes time and labor to manufacture the semiconductor light emitting device.